1. Field of the Invention
This invention generally relates to heating appliances and, more particularly, relates to gas-fueled heating appliances, both ventless, which vent combustion gases directly into the room in which the appliance is installed and vented, which vent combustion gases to atmosphere.
2. Description of the Related Art
Gas-fueled heating appliances, such as fireplaces, stoves, and fireplace inserts, have the cleanest exhaust of any combustion process and typically include a combustion chamber, or firebox, which is provided with a source of flammable gas. The flammable gas is then combusted to provide heat and aesthetic value to the room in which the appliance is installed. The combustion typically produces carbon monoxide, carbon dioxide, water, oxygen, nitrogen, nitrogen oxide, and carbon soot, which are vented away from the fireplace and to the outside environment through a flue network or chimney. The major constituents are oxygen, nitrogen, carbon dioxide, and water with significantly lower levels of carbon monoxide, nitrogen oxides, and carbon soot. The mercaptan odorant found in gas fuel oxidizes and forms sulfuric oxides. Although such gases are vented to atmosphere, causing no serious problems in the space adjoining the appliance, increasing concerns about the environment may bring this process under heavy scrutiny and eventual regulation.
In certain locations, it is desirable to have an appliance capable of operating without venting to the outside environment. Therefore, gas appliances have been designed which are clean burning but xe2x80x9cunventedxe2x80x9d in that the gas combusts and the products of the combustion are allowed to enter the room in which the appliance is installed. With such designs, a chimney or flue network is not necessary and consequently such designs can be placed in many locations which would otherwise not be able to accommodate a vented appliance.
Because such designs allow combustion gases to enter the room in which the fireplace is installed, any combustion products, such as carbon monoxide, and airborne particulates, are also exhausted from the appliance directly into the room in which the appliance is located.
In addition, with conventional unvented appliances, the combustion gases rise within the firebox and heat the top wall of the firebox before exiting into the room in which the fireplace is installed. If the heat is not controlled, this can potentially damage the top wall of the firebox or a mantle associated therewith.
U.S. Pat. No. 5,054,468, issued to Moon, discloses an unvented gas-fueled fireplace heater which vents all combustion gases and airborne particulates directly into the room in which the heater is installed, but does not include any means for reducing undesirable emissions.
U.S. Pat. No. 5,139,011, also issued to Moon, discloses an unvented gas-fueled fireplace heater which vents combustion gases and particulates directly to the ambient room air, and further includes a sensor which detects a low oxygen level and a gas supply switch which is activated by the oxygen sensor.
Early attempts at ventless appliances suffer from drawbacks such as: 1) water build-up in the space, 2) acid gases, such as nitrogen oxide and sulfuric oxide, are discharged into the space potentially causing respiratory distress and corrosion in the home, 3) excessive oxygen consumption, and 4) excessive build-up of carbon monoxide levels in the space.
The present invention is for use in either vented or unvented, gas-fueled, heating appliances and includes a system for reducing the amounts of undesirable combustion products which are released into the atmosphere or space in which the appliance is installed. However, the catalyst of the present invention is particularly useful in unvented applications, where the discharge and treatment of products of combustion is even more critical. The present invention also includes a system for inducing a draft to aspirate the combustion gases from the firebox, and thereby avoid thermal damage to the firebox or mantle.
In particular, the present invention provides a carbon monoxide catalyst element to oxidize the carbon monoxide released by the appliance into carbon dioxide before the combustion gases are vented into the atmosphere or ambient room air. The catalyst element also serves as a filter to screen airborne particulates, such as ceramic fibers dislodged from the synthetic logs disposed within the firebox of a fireplace.
The carbon monoxide catalyst element is disposed within a heating appliance which includes a firebox and a heat exchanger surrounding the firebox. In one embodiment, ambient air enters the heat exchanger through an opening on the bottom front of a fireplace, below the firebox, and is divided such that a portion of the ambient air enters the firebox through openings below gas burners disposed within the firebox, and the remaining portion proceeds through the heat exchanger along a plenum below the firebox, along an adjoining plenum behind the firebox, and then along an adjoining plenum above the firebox. The air within the heat exchanger then merges with combustion air being vented from the firebox, and the recombinant air then exits the fireplace through an opening at the top front of the fireplace.
The front face of the fireplace is enclosed with a glass window to assure complete venting of the combustion gases through the top of the firebox and heat exchanger plenum. The carbon monoxide catalyst element is disposed in the combustion gas exit located at the top of the firebox and the openings at the top and bottom front of the fireplace are covered by a grill, louvers, mesh, or other similar device.
The present invention induces a draft which assists in the aspiration of the combustion gases by drawing the combustion gases from the hot air, high pressure firebox to the cooler air, low-pressure heat exchanger and ambient environment of the room in which the appliance is installed. In addition to the natural draft created by the present design, the appliance can optionally include a blower within the heat exchanger to further assist the aspiration of the combustion gases and increase the thermal output of the appliance.
Moreover, the draft is of a sufficient velocity to aspirate the combustion gases from the firebox at a flowrate sufficiently high to avoid structural damage to the firebox top wall, or an associated mantle.
One advantage of the present invention is that it substantially reduces the amount of carbon monoxide and other gases released by the appliance into the atmosphere or room in which the appliance is installed.
Another advantage of the present invention is that it reduces the number of airborne particulates, such as ceramic fibers, released by the appliance into the room in which the appliance is installed.
Another advantage of the present invention is that the combustion gases are aspirated from the firebox at a rate sufficiently fast to avoid thermal damage to the firebox or an associated mantle.
Another advantage of the present invention is that pollutants from sources present in the space in which the heating appliance is located are destroyed when heated in the combustion chamber and passed through the catalyst.
A still further advantage of the present invention is that it provides an appliance which can be installed into any site regardless of the availability of a chimney or other venting medium.
The present invention, in one form thereof, provides a heating appliance comprising a firebox, a gas burner, a heat exchanger, and a carbon monoxide catalyst element. The firebox includes an outlet and the gas burner which produces products of combustion. The heat exchanger partially surrounds the firebox and a draft results from the firebox being under higher pressure than the heat exchanger. The draft aspirates the products of combustion away from the firebox. The carbon monoxide catalyst element is disposed within the firebox outlet, and oxidizes carbon monoxide contained within the products of combustion into carbon dioxide and prevents airborne particulates from exiting the firebox.
The present invention, in another form thereof, provides a carbon monoxide catalyst element for oxidizing carbon monoxide into carbon dioxide, and comprises a plurality of planar foils, a plurality of corrugated foils, a ceramic oxide coating, and a precious metal coating. The plurality of planar foils and the plurality of corrugated foils are manufactured from stainless steel with the corrugated foils being alternatingly interposed between the planar foils. The ceramic oxide and precious metal coatings are disposed on the plurality of planar foils and the plurality of corrugated foils.
The present invention, in yet another form thereof, provides an unvented, gas-fueled fireplace comprising a firebox, a gas burner, a heat exchanger, and a carbon monoxide catalyst element. The firebox includes an outlet with the gas burners being disposed within the firebox and producing products of combustion. The heat exchanger partially surrounds the firebox and draws ambient air in through an entrance provided below the firebox and exhausts convection heated air through an exit provided above the firebox. A draft results from the firebox being under higher pressure than the heat exchanger, with the draft aspirating the products of combustion away from the firebox and to the ambient environment through the heat exchanger exit. The carbon monoxide catalyst element is disposed within the draft and oxidizes carbon monoxide contained within the products of combustion into carbon dioxide and prevents airborne particulates from exiting the fireplace.
The present invention, in still another form thereof, provides an unvented gas-fueled stove comprising a firebox, a gas burner, a heat exchanger, a combustion gas circuit, and a carbon monoxide catalyst element. The firebox includes an outlet with the gas burner being disposed within the firebox and producing products of combustion. The heat exchanger partially surrounds the firebox and draws ambient air in through an entrance provided below the firebox and exhausts convection heated air through an exit provided above the firebox. The combustion gas circuit includes an inlet communicating ambient air to the firebox and an outlet communicating products of combustion out of the firebox. The carbon monoxide catalyst element is disposed within the combustion gas outlet and oxidizes carbon monoxide contained within the products of combustion into carbon dioxide and prevents airborne particulates from exiting the stove.